- Mean Time Between Repair. Similar in meaning to Mean Time Between
Failures (MTBF), and the two terms are sometimes
used interchangeably. MTBR is normally quoted for components which are
economically viable to repair should they fail. Whereas MTBF
is normally quoted for components for which it is not economically
viable to repair and which would therefore normally be replaced once
they have failed. For example a hard disk would not normally be
considered repairable should it fail, and thus manufacturers may quote a
MTBF figure. Whilst a RAID
array (which consists of multiple individual hard disks) would normally
have a MTBR figure quoted, because should any individual disk fail then
that disk can be replaced (and thus the array repaired).
The following definition has been suggested by Mike Strange: MTBR is the mean time between a repair action. There will a level of repair where the replaceable entity is not repairable, hence the "R" could be extrapolated to not only mean "Repair" but also "Replacement". Also starting with MTBF (Mean Time Between Failure, or the time between faults occurring), if the system under consideration has built-in redundancy then it will not necessarily mean that the system has to be repaired immediately; indeed it may not be possible in say an aircraft. It depends on whether one wishes to use the calculations for the purposes of spares provisioning or resourcing a repair facility; hence BER (Beyond Economic Repair) comes into play.